NZW30 rat-tat-tatting

After several years of functioning without a hitch, one of my NZW30 switches has started rat-tat-tatting after 4:00pm local time, and according to the hub to which it’s connnected (SmartThings), it’s unresponsive.

I have a recording of the sound, but I’m unable to upload it because I’m a “new user”.

Does anyone here have an idea as to what might be wrong?

TIA
Josh